<?php
// Add meta box
function sight_add_box() {
    global $meta_box;

    add_meta_box($meta_box['id'], $meta_box['title'], 'sight_show_box', $meta_box['page'], $meta_box['context'], $meta_box['priority']);
}

// Callback function to show fields in meta box
function sight_show_box() {
    global $meta_box, $post;

    // Use nonce for verification
    echo '<input type="hidden" name="sight_meta_box_nonce" value="', wp_create_nonce(basename(__FILE__)), '" />';

    echo '<table class="form-table">';

    foreach ($meta_box['fields'] as $field) {
        // get current post meta data
        $meta = get_post_meta($post->ID, $field['id'], true);

        echo '<tr>',
                '<th style="width:50%"><label for="', $field['id'], '">', $field['name'], '</label></th>',
                '<td>';
                echo '<input type="checkbox" name="', $field['id'], '" id="', $field['id'], '"', $meta ? ' checked="checked"' : '', ' />';
        echo     '<td>',
            '</tr>';
    }

    echo '</table>';
}

add_action('save_post', 'sight_save_data');

// Save data from meta box
function sight_save_data($post_id) {
    global $meta_box;

    // verify nonce
    if (!wp_verify_nonce($_POST['sight_meta_box_nonce'], basename(__FILE__))) {
        return $post_id;
    }

    // check autosave
    if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) {
        return $post_id;
    }

    // check permissions
    if ('page' == $_POST['post_type']) {
        if (!current_user_can('edit_page', $post_id)) {
            return $post_id;
        }
    } elseif (!current_user_can('edit_post', $post_id)) {
        return $post_id;
    }

    foreach ($meta_box['fields'] as $field) {
        $old = get_post_meta($post_id, $field['id'], true);
        $new = $_POST[$field['id']];

        if ($new && $new != $old) {
            update_post_meta($post_id, $field['id'], $new);
        } elseif ('' == $new && $old) {
            delete_post_meta($post_id, $field['id'], $old);
        }
    }
}
?>